Polarizing plate

ABSTRACT

A primary object of the present invention is to provide a polarizing plate excellent in durability. A polarizing plate (100) according to an embodiment of the present invention includes: a polarizer (10); and a protective film (21 and 22) arranged on at least one side of the polarizer (10). The polarizing plate (100) has a dimensional change ratio of −0.2% or more in a transmission axis direction thereof when the polarizing plate (100) cut into a size measuring 100 mm by 100 mm is bonded to a glass plate with a pressure-sensitive adhesive and the following operation is repeated 100 times: the polarizing plate (100) bonded to the glass plate is left to stand under an atmosphere at −40° C. for 30 minutes and then left to stand under an atmosphere at 85° C. for 30 minutes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. application Ser. No. 15/290,775 filed onOct. 11, 2016, which claims priority over Japanese application No.2015-216399 filed on Nov. 4, 2015, the entire contents of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a polarizing plate.

2. Description of the Related Art

A polarizing plate has been used in an image display apparatus (e.g., aliquid crystal display apparatus) of a cellular phone, a notebookpersonal computer, or the like. In recent years, the use of thepolarizing plate in, for example, a meter display portion of anautomobile or a smart watch has been desired, and hence the formation ofthe polarizing plate into a shape except a rectangular shape and theformation of a through-hole in the polarizing plate have been desired.However, when any such form is adopted, a problem in terms of durabilityis liable to occur. With a view to improving the durability, forexample, there has been proposed a method involving thermally treating apolarizer at a temperature of 95° C. or more, and laminating aprotective film on the thermally treated polarizer to provide apolarizing plate (see Japanese Patent Application Laid-open No. Hei7-333425). However, a further improvement in durability has beenrequired.

SUMMARY OF THE INVENTION

The present invention has been made to solve the problem, and a primaryobject of the present invention is to provide a polarizing plateexcellent in durability.

As a result of their extensive investigations, the inventors have paidattention to the fact that when a polarizing plate is bonded to anyother member (e.g., a glass plate) through intermediation of apressure-sensitive adhesive layer, the polarizing plate side of thepressure-sensitive adhesive layer is deformed (shrunk) by a change inexternal environment, and a stress produced by the deformation isrelated to the durability of the polarizing plate (the occurrence of acrack), and have found that when the dimensional change ratio of thepolarizing plate is controlled, the occurrence of a stress between therespective members is suppressed and hence the object can be achieved.Thus, the inventors have completed the present invention.

A polarizing plate according to an embodiment of the present inventionincludes: a polarizer; and a protective film arranged on at least oneside of the polarizer. The polarizing plate has a dimensional changeratio of −0.2% or more in a transmission axis direction thereof when thepolarizing plate cut into a size measuring 100 mm by 100 mm is bonded toa glass plate with a pressure-sensitive adhesive and the followingoperation is repeated 100 times: the polarizing plate bonded to theglass plate is left to stand under an atmosphere at −40° C. for 30minutes and then left to stand under an atmosphere at 85° C. for 30minutes. In one embodiment of the present invention, the polarizer has athickness of 20 μm or less. In one embodiment of the present invention,the polarizing plate is subjected to a heat treatment under conditionsof a temperature in a range of from 50° C. to 120° C. and a time periodof 1 hour or more and 100 hours or less. In one embodiment of thepresent invention, the polarizing plate has formed therein athrough-hole. In one embodiment of the present invention, the polarizingplate includes a site having an outer edge forming a substantiallyV-shape that is convex inward in a surface direction. In one embodimentof the present invention, the polarizing plate has the dimensionalchange ratio of 0.1% or less.

According to the present invention, the polarizing plate excellent indurability can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a polarizing plate according to one embodimentof the present invention.

FIG. 2 is a partially enlarged sectional view of the polarizing plateillustrated in FIG. 1.

FIG. 3 is a plan view of a polarizing plate according to anotherembodiment of the present invention.

FIG. 4A is a photograph for showing the periphery of a through-hole ofthe polarizing plate of Example 1 after a heat cycle test, FIG. 4B is aphotograph for showing the periphery of a through-hole of the polarizingplate of Example 2 after a heat cycle test, FIG. 4C is a photograph forshowing the periphery of a through-hole of the polarizing plate ofExample 3 after a heat cycle test, and FIG. 4D is a photograph forshowing the periphery of a through-hole of the polarizing plate ofComparative Example 1 after a heat cycle test.

FIG. 5A is a photograph for showing the state of the periphery of an endside of the polarizing plate along the transmission axis direction ofthe test sample of Example 1 after the heat cycle test, and FIG. 5B is aphotograph for showing the state of the periphery of an end side of thepolarizing plate along the absorption axis direction thereof.

FIG. 6A is a photograph for showing the state of the periphery of an endside of the polarizing plate along the transmission axis direction ofthe test sample of Comparative Example 1 after the heat cycle test, andFIG. 6B is a photograph for showing the state of the periphery of an endside of the polarizing plate along the absorption axis directionthereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described below. However, thepresent invention is not limited to these embodiments.

A. Polarizing Plate

FIG. 1 is a plan view of a polarizing plate according to one embodimentof the present invention, and FIG. 2 is a partially enlarged sectionalview of the polarizing plate illustrated in FIG. 1. A polarizing plate100 is suitably used in the meter panel of an automobile. The polarizingplate 100 includes a first display portion 50 and a second displayportion 60 that are continuously arranged, and through-holes 51 and 61for fixing various meter needles are formed around the centers of therespective display portions.

The diameter of each of the through-holes is, for example, from 0.5 mmto 100 mm. The outer edge of each of the display portions 50 and 60 isformed into an arc shape along the rotational direction of a meterneedle.

The polarizing plate 100 includes a polarizer 10, a first protectivefilm 21 arranged on one side of the polarizer 10, and a secondprotective film 22 arranged on the other side of the polarizer 10. Theprotective films 21 and 22 are each typically bonded to the surface ofthe polarizer 10 through intermediation of an adhesive layer, though thelayer is not shown. Although the protective films are arranged on bothsides of the polarizer in this illustrated example, a protective filmmay be arranged only on one side thereof.

The polarizing plate of the present invention has a dimensional changeratio in its transmission axis direction of −0.2% or more, preferably−0.1% or more, more preferably −0.05% or more when the polarizing plateis cut into a size measuring 100 mm by 100 mm and the cut polarizingplate is bonded to a glass plate with a pressure-sensitive adhesive, andin the state, the following operation is repeated 100 times (changeratio of a dimension after a heat cycle test to that before the test):the polarizing plate is left to stand under an atmosphere at −40° C. for30 minutes and then left to stand under an atmosphere at 8.5° C. for 30minutes. Meanwhile, the dimensional change ratio in the transmissionaxis direction is, for example, 0.1% or less. A polarizing platesatisfying such dimensional change ratio can have excellent durability.Specifically, the polarizing plate satisfying such dimensional changeratio shows an extremely small change in shape due to a change inexternal environment, and hence when the polarizing plate is bonded toany other member (e.g., the glass substrate of a liquid crystal cell orthe like) through intermediation of a pressure-sensitive adhesive layer,an influence on the adjacent pressure-sensitive adhesive layer isextremely small. Accordingly, a change in shape of thepressure-sensitive adhesive layer due to the change in externalenvironment is suppressed, and hence the occurrence of a stress betweenthe respective members (e.g., a stress produced when the modulus ofelasticity of the pressure-sensitive adhesive layer increases at lowtemperature) can be prevented. As a result, a crack does not occur inthe polarizing plate and hence the polarizing plate can have extremelyexcellent durability.

The dimensional change ratio in the absorption axis direction of thepolarizing plate after the heat cycle test to that before the test is,for example, from −0.6% to 0%. The dimensional change ratio may bedetermined from the following equation.

Dimensional change ratio (%)={(dimension after heat cycle test/dimensionbefore heat cycle test)−1}×100

When a through-hole is formed like the illustrated example, the positionof the through-hole may be appropriately set in accordance with, forexample, the applications of the polarizing plate. The crack is liableto occur by using the peripheral edge of the through-hole as a startingpoint, and the tendency may be more remarkable as the position of thethrough-hole becomes more distant from the outer edge of the polarizingplate. As a result, as the position of the through-hole becomes moredistant from the outer edge of the polarizing plate (e.g., its distancefrom the outer edge of the polarizing plate is 15 mm or more), adurability-improving effect exhibited by the fact that the dimensionalchange ratio is controlled can be more significantly obtained. As in theperipheral edge of the through-hole, a site whose outer edge forms aV-shape (including an R-shape) that is convex inward in a surfacedirection, such as a boundary portion 41 or 42 between the respectivedisplay portions, is also liable to be the starting point of the crack.

The polarizing plate of the present invention is not limited to theconstruction of the illustrated example and may be appropriatelychanged. For example, the shape of the polarizing plate, the presence orabsence of the through-holes, the shapes and sizes of the through-holes,and the number and formation positions of the through-holes may beappropriately changed. Specifically, there is given a mode in whichV-shaped portions 43 and 44 that are convex inward in the surfacedirection are formed so as to be adjacent to each other, and a notch 45is formed as illustrated in FIG. 3.

A-1. Polarizer

The polarizer typically includes a resin film containing a dichromaticsubstance. Examples of the dichromatic substance include iodine and anorganic dye. The substances may be used alone or in combination. Ofthose, iodine is preferably used.

Any appropriate resin may be used as a resin for forming the resin film.A hydrophilic resin (e.g., a polyvinyl alcohol (PVA)-based resin) ispreferably used as the resin. Examples of the PVA-based resin includepolyvinyl alcohol and an ethylene-vinyl alcohol copolymer. The polyvinylalcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinylalcohol copolymer is obtained by saponifying an ethylene-vinyl acetatecopolymer. The saponification degree of the PVA-based resin is typicallyfrom 85 mol % to 100 mol %, preferably 95.0 mol % or more, morepreferably 99.0 mol % or more, particularly preferably 99.93 mol % ormore. The saponification degree may be determined in conformity with JISK 6726-1994. The use of the PVA-based resin having such saponificationdegree can provide a polarizer excellent in durability.

The average polymerization degree of the PVA-based resin may beappropriately selected depending on purposes. The average polymerizationdegree is typically from 1,000 to 10,000, preferably from 1,200 to6,000, more preferably from 2,000 to 5,000. The average polymerizationdegree may be determined in conformity with JIS K 6726-1994.

The polarizer preferably shows absorption dichroism in the wavelengthrange of from 380 nm to 780 nm. The single axis transmittance (Ts) ofthe polarizer is preferably 40% or more, more preferably 41% or more,still more preferably 42% or more, particularly preferably 43% or more.A theoretical upper limit for the single axis transmittance is 50%, anda practical upper limit therefor is 46%. In addition, the single axistransmittance (Ts) is a Y value measured with the two-degree field ofview (C light source) of JIS Z 8701 and subjected to visibilitycorrection, and may be measured with, for example, a spectrophotometer(manufactured by JASCO Corporation, V7100). The polarization degree ofthe polarizer is preferably 99.8% or more, more preferably 99.9% ormore, still more preferably 99.95% or more.

The thickness of the polarizer may be set to any appropriate value. Thethickness is typically from 1 μm to 80 μm, preferably from 3 μm to 40μm. In one embodiment, the thickness of the polarizer is 20 μm or less,preferably 18 μm or less, more preferably 15 μm or less. The use of thepolarizer having such thickness can satisfactorily achieve thedimensional change ratio without performing a heat treatment to bedescribed later.

The polarizer may be typically obtained by subjecting the resin film totreatments, such as a swelling treatment, a stretching treatment, adyeing treatment with the dichromatic substance, a cross-linkingtreatment, a washing treatment, and a drying treatment. The number oftimes of each of the treatments, the order in which the treatments areperformed, the timings of the treatments, and the like may beappropriately set. When the resin film is subjected to each of thetreatments, the film may be a resin layer formed on a substrate.

The cross-linking treatment is performed by, for example, bringing aboric acid solution (e.g., an aqueous solution of boric acid) intocontact with the resin film. In addition, when a wet stretching systemis adopted in the stretching treatment, the stretching is preferablyperformed while a boric acid solution is brought into contact with theresin film. In ordinary cases, the resin film is uniaxially stretched atfrom 3 times to 7 times from the viewpoint that excellent polarizationcharacteristics are obtained. A stretching direction in the stretchingtreatment may correspond to the absorption axis direction of thepolarizer to be obtained. The transmission axis direction thereof may beperpendicular to the absorption axis direction. In one embodiment, whilean elongated resin film is conveyed in its lengthwise direction, thefilm is stretched in the conveying direction (MD). In this case, theabsorption axis direction of the polarizer to be obtained may be thelengthwise direction (MD), and the transmission axis direction thereofmay be a widthwise direction (TD).

A-2. Protective Film

As the formation materials of the protective film, there are given, forexample, a cellulose-based resin, such as diacetyl cellulose ortriacetyl cellulose (TAC), a (meth)acrylic resin, a cycloolefin-basedresin, an olefin-based resin, such as polypropylene, an ester-basedresin, such as a polyethylene terephthalate-based resin, apolyamide-based resin, a polycarbonate-based resin, and copolymer resinsthereof. The term “(meth)acrylic resin” refers to an acrylic resinand/or a methacrylic resin.

The thickness of the protective film is preferably from 10 μm to 200 μm.A surface-treated layer may be formed on one side of the protective film(side on which the polarizer is not arranged). Specifically, the sidemay be subjected to a hard coat treatment, an antireflection treatment,or a treatment intended for diffusion or anti-glaring. In addition, theprotective film may function as a retardation film. When the protectivefilms are arranged on both sides of the polarizer like the illustratedexample, the constructions (including a formation material and athickness) of both the films may be identical to each other, or may bedifferent from each other.

As described above, the protective film is typically bonded to thesurface of the polarizer through intermediation of the adhesive layer.Any appropriate adhesive may be adopted as an adhesive to be used in thebonding of the protective film. For example, an aqueous adhesive, asolvent-based adhesive, or an active energy ray-curable adhesive isused. An adhesive containing a PVA-based resin is preferably used as theaqueous adhesive.

B. Method of Producing Polarizing Plate

The polarizing plate of the present invention is produced by anyappropriate method as long as the dimensional change ratio can beachieved. In one embodiment, the polarizing plate of the presentinvention is produced by a method involving: preparing a polarizing filmlaminate including a polarizer and a protective film arranged on atleast one side of the polarizer; and shrinking the polarizing filmlaminate as required.

The polarizing film laminate is typically produced by bonding theprotective film to one side, or each of both sides, of the polarizer.

The polarizing film laminate is shrunk as required. The shrinkage of thepolarizing film laminate can provide a polarizing plate that cansatisfactorily achieve the dimensional change ratio irrespective of, forexample, the thickness of the polarizer. A method for the shrinkage istypically, for example, a method involving heating the polarizing filmlaminate. A heating temperature is, for example, from 50° C. to 120° C.,preferably from 70° C. to 90° C. When the temperature falls within suchrange, the polarizing film laminate can be efficiently shrunk while itsoptical characteristics (e.g., a hue, a transmittance, and apolarization degree) are secured. A heating time is, for example, from 1hour to 100 hours, preferably 2 hours or more, more preferably 10 hoursor more. The heating may be performed in one stage, or may be performedin a plurality of stages. In addition, the heating temperature may bekept substantially constant, or may be changed continuously or in astepwise manner.

A shrinkage ratio is preferably 0.2% or more, more preferably 0.3% ormore in, for example, the transmission axis direction of the polarizerin the polarizing film laminate. Meanwhile, the shrinkage ratio in thetransmission axis direction is, for example, 0.6% or less. With suchshrinkage ratio, it can be judged that the polarizing film laminate isshrunk to a sufficient level. The polarizing film laminate may shrink inits absorption axis direction to a larger extent than in thetransmission axis direction, and hence at the initial stage of theshrinkage, a dimension in the transmission axis direction of thepolarizing film laminate apparently increases for the time being in somecases. In any such case, as the shrinkage progresses, the dimension inthe transmission axis direction may reduce from a dimension at the timeof the initiation of the shrinkage (at the time of the initiation of theheating).

A shrinkage ratio in the absorption axis direction of the polarizingfilm laminate is preferably 0.3% or more, more preferably 0.4% or more.Meanwhile, the shrinkage ratio in the absorption axis direction is, forexample, 1.0% or less. The shrinkage ratio may be determined from thefollowing equation.

Shrinkage ratio (%)={1−(dimension after heating/dimension beforeheating)}×100

The polarizing plate of the present invention can be formed into adesired shape because the polarizing plate has excellent durability. Amethod of forming the polarizing plate into the desired shape istypically, for example, a method involving cutting (punching) thepolarizing film laminate. When the polarizing film laminate is shrunk,the cutting may be performed before the shrinkage, or may be performedafter the shrinkage. The cutting is preferably performed after theshrinkage from the viewpoint that the forming into the desired shape isperformed more accurately.

Any appropriate method may be adopted as a cutting (punching) method.For example, a method involving irradiating the laminate with laserlight or a method involving using a cutting blade (punching die), suchas a Thomson blade or a pinnacle blade, is given. The laser lightirradiation provides a smooth cut surface and can suppress theoccurrence of the starting point of a crack (initial crack), and hencecan contribute to a further improvement in durability. Even when thecutting blade is used (even when the initial crack occurs), thedimensional change ratio is controlled and hence excellent durabilitycan be obtained.

Any appropriate laser may be adopted as the laser as long as thepolarizing film laminate (polarizing plate) can be cut. A laser that canemit light having a wavelength in the range of from 150 nm to 11 μm ispreferably used. Specific examples thereof include a gas laser, such asa CO₂ laser, a solid laser, such as an YAG laser, and a semiconductorlaser. Of those, a CO₂ laser is preferably used.

A condition for the laser light irradiation may be set to anyappropriate condition depending on, for example, the laser to be used.When the CO₂ laser is used, an output condition is preferably from 10 Wto 1,000 W, more preferably from 100 W to 400 W.

C. Usage

The polarizing plate of the present invention is bonded to any othermember (e.g., the glass substrate of a liquid crystal cell or the like)through intermediation of, for example, a pressure-sensitive adhesivelayer. The thickness of the pressure-sensitive adhesive layer ispreferably from 4 μm to 50 μm. An acrylic pressure-sensitive adhesive ispreferably used as a pressure-sensitive adhesive forming thepressure-sensitive adhesive layer. The polarizing plate of the presentinvention may adopt the form of a polarizing plate with apressure-sensitive adhesive layer having the pressure-sensitive adhesivelayer arranged on at least one side thereof in advance.

Now, the present invention is specifically described by way of Examples.However, the present invention not limited to these Examples.

EXAMPLE 1 (Production of Polarizing Film Laminate Sheet)

A film (thickness: 28 μm) obtained by incorporating iodine into anelongated PVA-based resin film and uniaxially stretching the film in itslengthwise direction (MD) was used as a polarizer.

A PVA-based adhesive was applied to one side of the polarizer so thatits thickness after drying became 100 nm, and an elongated TAC filmhaving a thickness of 40 μm was bonded to the polarizer so that theirlengthwise directions were aligned with each other.

Subsequently, a PVA-based adhesive was applied to the other side of thepolarizer so that its thickness after drying became 100 nm, and anelongated acrylic film having a thickness of 30 μm was bonded to thepolarizer so that their lengthwise directions were aligned with eachother.

Thus, a polarizing film laminate sheet having a construction “TACfilm/polarizer/acrylic film” was obtained.

The resultant polarizing film laminate sheet was cut with a CO₂ laser(wavelength: 9.35 μm, output: 150 W) to provide a cut piece of a sizemeasuring 112 mm by 112 mm, the cut piece having a through-hole having adiameter of 2 mm formed in a site distant from its outer edge by 55 mm.

The resultant cut piece was placed under an atmosphere at 85° C. for 50hours to provide a polarizing plate. The polarizing plate had ashrinkage ratio in its absorption axis direction of 0.74% and ashrinkage ratio in its transmission axis direction of 0.44%, theshrinkage ratios each serving as a ratio of a dimension after theheating to that before the heating. The shrinkage ratios each serving asa ratio of a dimension after the heating to that before the heating wereeach determined by: separately preparing a cut piece cut out of thepolarizing film laminate sheet into a size measuring 100 mm by 100 mm(no through-hole was formed in the cut piece); and measuring theposition of a corner of the cut piece. In this case, the cut piece wascut out of the sheet so that a pair of sides opposite to each othercorresponded to the transmission axis direction of the polarizer andanother pair of sides opposite to each other corresponded to theabsorption axis direction of the polarizer.

EXAMPLE 2

A polarizing plate was obtained in the same manner as in Example 1except that the resultant cut piece was placed under an atmosphere at85° C. for 5 hours. The polarizing plate had a shrinkage ratio in itsabsorption axis direction of 0.45% and a shrinkage ratio in itstransmission axis direction of 0.37%, the shrinkage ratios each servingas a ratio of a dimension after the heating to that before the heating,and each being measured by the same method as that of Example 1.

EXAMPLE 3

A polarizing plate was obtained in the same manner as in Example 1except that the resultant cut piece was placed under an atmosphere at85° C. for 2.5 hours. The polarizing plate had a shrinkage ratio in itsabsorption axis direction of 0.34% and a shrinkage ratio in itstransmission axis direction of 0.25%, the shrinkage ratios each servingas a ratio of a dimension after the heating to that before the heating,and each being measured by the same method as that of Example 1.

EXAMPLE 4

A polarizing plate was obtained in the same manner as in Example 1except that: the size of the cut piece was set to 52 mm by 52 mm; andthe through-hole was formed in a site distant from the outer edge of thecut piece by 25 mm.

EXAMPLE 5

A polarizing plate was obtained in the same manner as in Example 1except that at the time of the production of the polarizing filmlaminate sheet, a polarizer having a thickness of 12 μm was used and thecut piece was not heated.

EXAMPLE 6

A polarizing plate was obtained in the same manner as in Example 1except that at the time of the production of the polarizing filmlaminate sheet, a polarizer having a thickness of 18 μm was used, a TACfilm having a thickness of 60 μm was used instead of the acrylic filmhaving a thickness of 30 μm, and the cut piece was not heated.

COMPARATIVE EXAMPLE 1

A polarizing plate was obtained in the same manner as in

Example 1 except that the cut piece was not heated.

COMPARATIVE EXAMPLE 2

A polarizing plate was obtained in the same manner as in Example 4except that the cut piece was not heated.

The durability of each of the resultant polarizing plates was evaluatedby a heat cycle (HC, heat shock (HS)) test.

Specifically, each of the resultant polarizing plates was bonded to aglass plate with an acrylic pressure-sensitive adhesive (thickness: 20μm) having a difference between a storage modulus of elasticity in ahigh-temperature region (85° C.) and a storage modulus of elasticity ina low-temperature region (−40° C.) of less than 1×10⁹ Pa, having astorage modulus of elasticity at 25° C. of 1×10⁵ Pa or more, and havinga storage modulus of elasticity at 85° C. of less than 1×10⁶ Pa. Thus, atest sample was obtained. The storage moduli of elasticity are eachdetermined by performing measurement with a dynamicviscoelasticity-measuring apparatus (manufactured by RheometricScientific, “Advanced Rheometric Expansion System (ARES)”) under thecondition of a frequency of 1 Hz in the range of from −70° C. to 200° C.at a rate of temperature increase of 5° C./min to calculate a shearstorage modulus.

The resultant test sample was left to stand under an atmosphere at −40°C. for 30 minutes and then left to stand under an atmosphere at 85° C.for 30 minutes. The foregoing operation was defined as one cycle and thecycle was repeated 100 times. After the heat cycle test, whether or nota crack occurred in the polarizing plate was observed.

In addition, the change ratio of a dimension in the transmission axisdirection of the polarizing plate after the heat cycle test to thatbefore the test was measured. The dimensional change ratio wasdetermined by: separately preparing a cut piece cut out of thepolarizing film laminate sheet (in each of Examples 1 to 4, out of thepolarizing film laminate sheet heated in advance) into a size measuring100 mm by 100 mm (no through-hole was formed in the cut piece);subjecting the cut piece to the heat cycle test; and measuring theposition of a corner of the cut piece. In this case, the cut piece wascut out of the sheet so that a pair of sides opposite to each othercorresponded to the transmission axis direction of the polarizer andanother pair of sides opposite to each other corresponded to theabsorption axis direction of the polarizer.

The dimensional change ratios of Examples and Comparative Examples aresummarized in Table 1.

TABLE 1 Dimensional change ratio (%) Example 1 0.007 Example 2 −0.08Example 3 −0.14 Example 4 0.007 Example 5 −0.15 Example 6 −0.15Comparative Example 1 −0.37 Comparative Example 2 −0.37

FIG. 4A to FIG. 4D are photographs obtained by observing the peripheriesof the through-holes of the polarizing plates of Examples 1 to 3 andComparative Example 1 after the HS tests with an optical microscope(manufactured by Olympus Corporation, MX61, magnification: 5). InComparative Example 1, a crack that can be visually recognized with theeyes in a clear manner is observed. In contrast, in Example 1, theoccurrence of a crack (including a microcrack) is not observed. In eachof Examples 2 and 3, a microcrack that cannot be visually recognizedwith the eyes in a clear manner is observed, but the occurrence of acrack is suppressed as compared to Comparative Example 1. The crackseach occur along a stretching direction.

In Example 4, as in Example 1, the occurrence of a crack (including amicrocrack) is not observed. In Comparative Example 1, the crack extendsfrom the through-hole serving as a starting point to an end side of thepolarizing plate. In contrast, in Comparative Example 2, a crack lengthis 12 mm.

In each of Examples 5 and 6, as in Example 1, the occurrence of a crack(including a microcrack) is not observed.

FIG. 5A and FIG. 5B are each a photograph for showing the state of anend portion of the polarizing plate of the test sample of Example 1after the HS test, and FIG. 6A and FIG. 6B are each a photograph forshowing the state of an end portion of the polarizing plate of the testsample of Comparative Example 1 after the HS test. In ComparativeExample 1, a region in which the pressure-sensitive adhesive layer usedat the time of the bonding of the polarizing plate to the glass plate isexposed is formed.

The polarizing plate of the present invention can be suitably used notonly in an image display apparatus (a liquid crystal display apparatusor an organic EL device) of a rectangular shape but also in, forexample, an image display portion of a particular shape typified by themeter display portion of an automobile or a smart watch.

What is claimed is:
 1. A polarizing plate, comprising: a polarizer; and a protective film arranged on at least one side of the polarizer, wherein the polarizer has a thickness of 20 μm or less, wherein the polarizing plate has a dimensional change ratio of −0.2% or more in a transmission axis direction thereof; wherein the dimensional change ratio is measured by cutting the polarizing plate to 100 mm by 100 mm while bonded to a glass plate with a pressure-sensitive adhesive and an operation wherein the polarizing plate bonded to the glass plate is left to stand under an atmosphere at −40° C. for 30 minutes and then left to stand under an atmosphere at 85° C. for 30 minutes, is repeated 100 times.
 2. The polarizing plate according to claim 1, wherein the polarizing plate has the dimensional change ratio of 0.1% or less.
 3. A polarizing plate, comprising: a polarizer; and a protective film arranged on at least one side of the polarizer, wherein the polarizer has a thickness of 20 μm or less, wherein the polarizing plate has a dimensional change ratio of −0.2% or more in a transmission axis direction thereof; wherein the dimensional change ratio is measured by cutting the polarizing plate to 100 mm by 100 mm while bonded to a glass plate with a pressure-sensitive adhesive and an operation wherein the polarizing plate bonded to the glass plate is left to stand under an atmosphere at −40° C. for 30 minutes and then left to stand under an atmosphere at 85° C. for 30 minutes, is repeated 100 times, and the polarizing plate has one selected from the group consisting of a through-hole formed therein, a site having an outer edge forming a substantially V-shape that is convex inward in a surface direction, and the combination of the through-hole and the site.
 4. A polarizing plate, comprising: a polarizer; and a protective film arranged on at least one side of the polarizer, wherein the polarizing plate has a dimensional change ratio of −0.2% or more in a transmission axis direction thereof; wherein the dimensional change ratio is measured by cutting the polarizing plate to 100 mm by 100 mm while bonded to a glass plate with a pressure-sensitive adhesive and an operation wherein the polarizing plate bonded to the glass plate is left to stand under an atmosphere at −40° C. for 30 minutes and then left to stand under an atmosphere at 85° C. for 30 minutes, is repeated 100 times, and the polarizing plate has one selected from the group consisting of a through-hole formed therein, a site having an outer edge forming a substantially V-shape that is convex inward in a surface direction, and the combination of the through-hole and the site.
 5. The polarizing plate according to claim 1, further comprising a second protective film, wherein the second protective film is arranged on another side of the polarizer that is opposite to the protective film.
 6. The polarizing plate according to claim 1, wherein the polarizing plate has the dimensional change ratio of −0.1 to 0.1%.
 7. The polarizing plate according to claim 1, wherein the polarizing plate has a dimensional change ratio of −0.6 to 0% in an absorption axis direction, wherein the dimensional change ratio in an absorption axis direction is measured by cutting the polarizing plate to 100 mm by 100 mm while bonded to a glass plate with a pressure sensitive adhesive and an operation wherein the polarizing plate bonded to the glass plate is left to stand under an atmosphere at −40° C. for 30 minutes and then left to stand under an atmosphere at 85° C. for 30 minutes, is repeated 100 times.
 8. The polarizing plate according to claim 3, further comprising a second protective film, wherein the second protective film is arranged on another side of the polarizer that is opposite to the protective film.
 9. The polarizing plate according to claim 3, wherein the polarizing plate has the dimensional change ratio of −0.1 to 0.1%.
 10. The polarizing plate according to claim 3, wherein the polarizing plate has a dimensional change ratio of −0.6 to 0% in an absorption axis direction, wherein the dimensional change ratio in an absorption axis direction is measured by cutting the polarizing plate to 100 mm by 100 mm while bonded to a glass plate with a pressure sensitive adhesive and an operation wherein the polarizing plate bonded to the glass plate is left to stand under an atmosphere at −40° C. for 30 minutes and then left to stand under an atmosphere at 85° C. for 30 minutes, is repeated 100 times.
 11. The polarizing plate according to claim 4, further comprising a second protective film, wherein the second protective film is arranged on another side of the polarizer that is opposite to the protective film.
 12. The polarizing plate according to claim 4, wherein the polarizing plate has the dimensional change ratio of −0.1 to 0.1%.
 13. The polarizing plate according to claim 4, wherein the polarizing plate has a dimensional change ratio of −0.6 to 0% in an absorption axis direction, wherein the dimensional change ratio in an absorption axis direction is measured by cutting the polarizing plate to 100 mm by 100 mm while bonded to a glass plate with a pressure sensitive adhesive and an operation wherein the polarizing plate bonded to the glass plate is left to stand under an atmosphere at −40° C. for 30 minutes and then left to stand under an atmosphere at 85° C. for 30 minutes, is repeated 100 times. 